Role of primer in rubber to nylon 6,6 bonding

Primers are often used in rubber to metal bonding to protect the bonded area against corrosion in service. Their role in rubber to nylon 6,6 bonding was studied by means of peel tests. Test-pieces in the form of bonded strips were prepared by vulcanising a natural rubber compound containing 60 parts per hundred rubber by weight (p.p.h.r.) high abrasion furnace carbon black in contact with nylon 6,6 substrates. Proprietary organic solvent-based or water-based primer and covercoat bonding agents were used for bonding the rubber. Peel tests were performed under constant load at an angle of 90° and at ambient temperature (∼23°C). When rubber was peeled, bond failure was cohesive in the primer and in the rubber as well as at the primer/nylon interface. Interestingly, when rubber was bonded to nylon using organic solvent-based or water-based covercoat and peeled under similar test condition, bond failure was cohesive in the rubber and the strength of the bond improved noticeably.